459 research outputs found
Use of scrap tires in civil engineering applications
Using scrap tires as construction materials in civil engineering is of growing interest. Whole scrap tires have been used as culverts, retaining walls, and for slope and beach stabilization. Shredded tires have been used as horizontal drains, ravine crossings, highway embankments, lightweight backfill, and road bed support. The practice of these applications needs the engineering properties of scrap tires. This dissertation involves the quantification of the structural and hydraulic properties of whole truck tires as underground culverts, the derivation of a new stress-strain relationship for low-stiffness flexible pipes and its application to a truck tire culvert, and the investigation and integration of the mechanical properties of shredded tire material. The design guidelines for truck tire culverts developed in this research are also included
High-Order Harmonic Generation and Molecular Orbital Tomography: Characteristics of Molecular Recollision Electronic Wave Packets
We investigate the orientation dependence of molecular high-order harmonic
generation (HHG) both numerically and analytically. We show that the molecular
recollision electronic wave packets (REWPs) in the HHG are closely related to
the ionization potential as well as the particular orbital from which it
ionized. As a result, the spectral amplitude of the molecular REWP can be
significantly different from its reference atom (i.e., with the same ionization
potential as the molecule under study) in some energy regions due to the
interference between the atomic cores of the molecules. This finding is
important for molecular orbital tomography using HHG[Nature \textbf{432},
867(2004)].Comment: 4 pages, 4 figure
Stable knots in the trapped Bose-Einstein condensates
The knot of spin texture is studied within the two-component Bose-Einstein
condensates which are described by the nonlinear Gross-Pitaevskii equations. We
start from the non-interacting equations including an axisymmetric harmonic
trap to obtain an exact solution, which exhibits a non-trivial topological
structure. The spin-texture is a knot with an integral Hopf invariant. The
stability of the knot is verified by numerically evolving the nonlinear
Gross-Pitaevskii equations along imaginary time.Comment: 4 pages, 5 figure
Thermodynamical properties of a trapped interacting Bose gas
The thermodynamical properties of interacting Bose atoms in a harmonic
potential are studied within the mean-field approximation. For weak
interactions, the quantum statistics is equivalent to an ideal gas in an
effective mean-field potential. The eigenvalue of the Gross-Pitaevskii equation
is identified as the chemical potential of the ideal gas. The condensation
temperature and density profile of atoms are calculated. It is found that the
critical temperature decreases as the interactions increase. Below the
critical point, the condensation fraction exhibits a universal relation of
, with the index independent of
the interaction strength, the chemical potential, as well as the frequency of
the confining potential.Comment: 5 figures, Accepted by Mod. Phys. Lett. B. arXiv admin note: text
overlap with arXiv:cond-mat/0001079 by other author
Disorder effects on the quantum coherence of a many-boson system
The effects of disorders on the quantum coherence for many-bosons are studied
in a double well model. For the ground state, the disorder enhances the quantum
coherence. In the deep Mott regime, dynamical evolution reveals periodical
collapses and revivals of the quantum coherence which is robust against the
disorder. The average over variations in both the on-site energy and the
interaction reveals a beat phenomenon of the coherence-decoherence oscillation
in the temporal evolution.Comment: 4 figure
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